Which long-acting barbiturate is used as an oral anticonvulsant for idiopathic epilepsy in dogs?

• A. Phenobarbital
• B. Methohexital
• C. Pentobarbital
• D. Diazepam

Answer: (A)

Phenobarbital is the long-acting barbiturate used for ongoing oral anticonvulsant therapy in dogs with idiopathic epilepsy because it provides stable, daily seizure control when given by mouth. It enhances GABAergic inhibition by increasing the duration of chloride channel opening at GABA-A receptors, which dampens neuronal excitability across the brain and raises the seizure threshold. Its long-lasting action supports regular twice-daily dosing and it has the most extensive clinical evidence for canine epilepsy management. However, it can affect the liver, so dogs on phenobarbital require regular liver function monitoring and dose adjustments to keep levels within a therapeutic range. The other options aren’t suitable for chronic oral control: methohexital is a very short-acting anesthetic, pentobarbital is typically used for short-term seizure management or euthanasia rather than maintenance therapy, and diazepam is a benzodiazepine, not a barbiturate, and is not used for long-term seizure control in dogs.